BGA connectors are used in many applications where a low-profile, high-density electrical connector is desired or required. A typical BGA connector comprises a receptacle, and a header that mates with the receptacle. The header can have a plurality of through holes formed therein A plurality of male contacts are positioned within the through holes. The male contacts mate with female contacts of the receptacle to establish electrical contact between the header and the receptacle.
Each male contact of the header can have a ball-shaped piece of solder material fixed to an end thereof. The solder balls are located directly below the housing, and form a grid array. The header is mounted on a circuit substrate by aligning the grid array with a corresponding array of electrical contact points, e.g., solder pads, on a surface of the substrate. Heated gas, e.g., air, is subsequently directed over the header to melt the solder balls and form a solder joint between each male contact and a corresponding solder pad (this process is commonly referred to as “solder reflow”).
The substrate, in general, must be substantially horizontal and the mounting surface must be facing upward during the solder reflow process. This requirement is generated by the need to ensure that the liquefied solder from each solder ball flows onto (and remains on) the corresponding solder pad on the mounting surface. Hence, a second header, in general, cannot be mounted on a second surface of the substrate while the first header is being secured to an opposing first surface thereof. Instead, the substrate must be rotated (flipped) after the first header has been mounted so that the second surface is facing upward as the second header is mounted. Hence, the first header is suspended (hangs) from the first surface by the newly-formed solder joints on the first surface while the second header is mounted on the second surface.
Mounting a first and a second header in the above-noted manner presents difficulties. In particular, the heated gas used to melt (reflow) the solder balls of the second header also heats the newly formed solder joints on the first surface. This heating, in conjunction with the stresses in the solder joints caused by suspending the first header therefrom, can weaken and, in extreme cases, can melt the solder joints. This problem is particularly troublesome in applications where the headers being mounted are relatively heavy.